Christine Hall, who is 5 foot 4 inches tall, said she went from weighing 190 pounds to 114 pounds during a two-year period by tracking the calories online for food she bought at her nearby Starbucks, NBCNews.com reported.
The 66-year-old librarian, who lives in Alexandria, Va., said she planned her meals one day in advance because she memorized the calories for everything on the Starbucks menu.
Hall said she's eating a healthy variety of foods -- mixing protein, fruit and vegetables with her doctor's approval. For example, a daily menu could consist of oatmeal for breakfast and a 5-calorie cup of coffee, a "bistro box" with fruit and cheese for lunch and panini for dinner.
The Roasted Vegetable Panini -- one of several panini's Starbucks offers -- has 350 calories for its roasted zucchini, eggplant and red peppers with baby spinach and provolone cheese on focaccia bread.
Registered dietitian Amy Jamieson-Petonic said there's no doubt Hall was successful losing weight when she often ate as little as 876 calories a day.
However, Jamieson-Petonic told NBC's TODAY.com it's one thing to choose low-calorie foods, but another to choose low-calorie foods that are nutritionally balanced. She suggested preparing meals at home using legumes, brown rice, whole grains and frozen fruit and vegetables to "stretch your food dollars" because eating out can be costly.
Notable deaths of 2014 [PHOTOS]